Abstract: Objective To investigate polymorphisms and genotypic characteristics of the 16S-23S rDNA Internal Transcribed Spacer (ITS) regions of Burkholderia pseudomallei strains isolated in Hainan province and understand the difference in genetic background between B.pseudomallei strains of Hainan and other melioidosis-endemic areas worldwide.Methods ITS fragments of 272 B.pseudomallei strains from Hainan were amplified by PCR and the length of products were detected with capillary gel electrophoresis.Genotypes and sequence consistency of distinct lengths of ITSs were confirmed by DNA sequencing and alignment,and 2 tests were used to evaluate the distributional difference of ITS types between Hainan strains and the strains from other melioidosis-endemic areas.Results By using the methods of capillary electrophoresis and DNA sequencing,we identified 4 genotypes of ITS (C,E,CE,G) among 272 strains of B.pseudomallei,including 64 strains of type C (23.53%),144 strains of type E (52.94%),56 strains of type CE (20.59%) and 8 strains of type G (2.94%).Sequence alignment showed that DNA sequences for each of three ITS types (C,E,G) in Hainan were conserved and that length difference between ITS types should be attributed to the sequential variations within the major region of variability of ITS.The difference in ITS genotype distributions were significant between Hainan strains and Thailand strains (2=8.296,P0.05),but no such significant difference was found between Hainan strains and Australia strains (2=5.521,P0.05).Conclusion Four ITS genotypes (C,E,CE and G) were observed in B.pseudomallei strains of Hainan,among which C,E,CE were predominant.Compared with other melioidosis-endemic areas,such as Thailand and Australia,Hainan has a higher proportion of type G strains.